The present invention relates broadly to methods and apparatus for yarn preparation by mechanical deformation and, more particularly, to a method and apparatus increasing the yield of rubber yarn for by stretching prior to winding.
Natural rubber yarn, in the form of strands, is incorporated into various textile base yarns to increase the stretchability thereof. Incorporation of a natural rubber yarn into a loose knit or weave can provide the resulting fabric with the ability to return to its original configuration after being stretched. One of the problems with natural rubber yarn is its tendency to after stretching. That is, after a number of stretch and relax cycles, the rubber yarn increases, the yarn elongates and it no longer returns to its original form. This inherent, troublesome characteristic makes working with natural rubber yarn difficult. The yarn must be prestretched prior to use or the resultant fabric will have less than ideal stretching characteristics.
It has been empirically determined that natural rubber yarn will achieve a stability with respect to plastic deformation after three stretches. For a continuous, traveling strand, the effect is pronounced over whatever segment of natural rubber yarn is stretched. This stretching acts to break weaker bonds within the rubber which would be broken in any event under use. Therefore, if rubber yarn can be stretched and allowed to relax three times prior to use, the yarn would be much more stable and would provide a better finished product.
Accordingly, there exists a need for a method and apparatus to prestretch rubber yarn prior to use, and, preferably, relatively early in the fabric manufacturing process.